Abstract
Chinese kale (Brassica oleracea var. alboglabra) is rich in carotenoids, and neoxanthin is one of the most important carotenoids in Chinese kale. In this study, the function of the neoxanthin synthase gene (BoaNXS) in Chinese kale was investigated. BoaNXS, which had a 699-bp coding sequence, was cloned from the white flower cultivar of Chinese kale and was expressed in all developmental stages and organs of Chinese kale; its expression was highest in young seeds. The subcellular localization indicated that BoaNXS was localized in the chloroplast. BoaNXS-overexpressed plants were obtained via Agrobacterium-mediated transient overexpression methodology, and the gene overexpression efficiencies ranged from 2.10- to 4.24-fold. The color in the leaves of BoaNXS-overexpressed plants changed from green to yellow-green; the content of total and individual carotenoids, such as neoxanthin, violaxanthin, and lutein, was significantly increased, and the expression levels of most carotenoid biosynthetic genes were notably increased. These findings indicated that BoaNXS is of vital importance in carotenoid biosynthesis in Chinese kale and could be used as a candidate gene for enriching the carotenoid accumulation and color of Chinese kale and other Brassica vegetables.
Highlights
Carotenoids are a major group of pigments that are distributed abundantly in a variety of plants [1]
The same effect was observed in carrot where transcripts of endogenous Dcpsy1, Dcpsy2, and Dclcyb2 genes were increased when Dclcyb1 was overexpressed [36]. These results indicated that overexpression of BoaNXS induced a positive feedback loop affecting the expression of genes involved in carotenoid biosynthesis
The neoxanthin synthase gene BoaNXS was cloned, and BoaNXS was located in the chloroplast
Summary
Carotenoids are a major group of pigments that are distributed abundantly in a variety of plants [1] They typically contain 40 carbons in their polyene backbones with conjugated double bonds and rings at the ends [2]. The accumulation of carotenoids enhances both the sensory and nutritional quality of fruits, flowers, and vegetables; carotenoids are beneficial to human health [5]. They are essential precursors to several phytohormones, such as abscisic acid and strigolactones [6]. The carotenoid biosynthesis pathway in higher plants consists of the condensation of small molecular substances into C40 compounds and a series of reactions, including dehydrogenation, isomerization, cyclization, hydroxylation, and epoxidation, to produce different carotenoids [8]
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